This isn't tertiary it's secondary as stated and labelled at 5:59 , since yes it's connected to two other carbons.
What Ari was referring to was that Elimination reactions, both E1 and E2, favor tertiary and secondary alkyl halides. The wedged doesn't do anything here it's just showing stereochemistry which doesn't matter here since elimination just changes the product to an alkene. The stereochemistry (wedged or dashed) matters when we are doing substitution reactions since we will either have inversion (SN2) or both inversion and retention (racemization, SN1).
Yes the formation of cyclopropanes is the same thing as cyclopropanation. Your lecture notes just show a more complex structure. But the overall concept is still the same, we start with an alkene and use a carbene to form the cyclopropane.
At this time we don't have downloads of these reaction summaries but you can find the video review and reaction summaries of several functional groups here in the below video. Check the timestamps in the description for each reaction summary.